Cold-drawn alloy steel wire which can be hot dip coated with aluminum



United States Patent-Q 3,404,969 COLD-DRAWN ALLOY STEEL WIRE WHICH CAN BE HOT DIP COATED WITH ALUMINUM Alvin W. Holmes, Muncie, lnd., assignor to General Cable Corporation, New York, N.Y.', a corporation of NewJersey No Drawing. Continuation-impart of application Ser. No. 391,280, Aug. 21, 1964. This application Oct. 12, 1967, Ser. No. 674,714 a '14 Claims. (Cl. 29-1962) ABSTRACT OF THE DISCLOSURE A cold drawn, carbon steel wire which consists essentially of 0.5% to 1.0% carbon, 0.03% to 0.5% of a metal selected from the group of chromium, tungsten, molybdenum, vanadium and columbium, and the balance iron. The cold drawn Wire may be subjected to temperatures of approximately 800 F. to l300 F. in the course of hot dip coating of the wire with aluminum. The normal loss of tensile strength due to the exposure of the Wire to said temperatures is reduced, by virtue of the chemical composition of the wire combined with the severe cold working to which it has beensubjected.

CROSS REFERENCES This is a continuation-in-part of my copending application Ser. No. 391,280, filed Aug. 21, 1964, now abandoned.

BACKGROUND OF THE INVENTION electrical conductor of the type employed in over-head transmission lines. To reduce corrosion in such conductors, it is common to apply an aluminum coating to the steel core, usually by passing the core wire through a bath of molten aluminum maintained at a temperature of 1200" F. to 1300 F. Such a process can result in lowering the tensile strength of a conventional cold-drawn, carbon steel wire from, for example, a value above 295,000 p.s.i. to a value below 190,000 p.s.i. The latter value is objectionably close to the minimum tensile strength required in the steel core-wires of presentday stranded aluminum conductors, steel reinforced (A.C.S.R.). Because of the strength-loss resulting from the annealing incident to the coating of steel wires in a molten bath of aluminum or other metal, attempts have been made to obtain adequate strength in the coated wire by increasing the carbon content of the wire; but since increasing carbon content is accompanied by de creasing ductility, such attempts have failed to produce wholly satisfactory results.

It is'an object'of-this invention to reduce the drop in tensilenstrength produced by relatively high-temperature annealing of colddrawn,'carbon steel Wires and to produce awire which, after being subject to such annealing, will possess a tensile strength substantially higher than that of conventional wires similarly treated.

namely,

3 #104,969 Oct, 8, 1068 SUMMARY OF THE INVENTION I have found that the decrease in tensile strength which results from treating cold-drawn, carbon steel wire'at temperatures in the neighborhood of 800 F. upwards can be substantially reduced by incorporating in the steel a small portion of a suitablealloying metal. Of the alloying metals more or less commonly employed in steels nickel, silicon, aluminum, zirconium, manganese, chromium, tungsten, molybdenum, vanadium, columbium, titanium, pp d. l h one wh ch, ha e; the effect I desire are those which fall in Groups V-B and VI-B of the Periodic Table" (Periodic Chart of the Elements, Fisher Scientific Company, appearing in Handbook of Chemistry and Physics, 1952-53 edition, published by Chemical Rubber Publishing Cof) andwhich wire. For example,inone steel of core-wiregrade, the

addition of 0.08% vanadium reduced the tensile strength from 283,000 p.s.i. to 253,000 p.s.i. in the wire as colddrawn, but increased tensile strength from 187,000 p.s.i. to 196,O00p.s.i.' in the'wire as annealed'fortenseconds at 1230 F. In another core-wire steel, the addition-of 0.33% molybdenum reduced the tensile strength ofthe tifiatiiiealedfh ai'tl-drawn wire from Z98,000 'p .siifto259,- 000 p.s.i., but increased that of the annealed wire from 195,000 p.s.i. to 202,000.p.s.i. V

. The e fe t Qfjhe carb de-tan in elem nt inredu iu the loss of strength due to annealing of the colddrawn wire becomes more pronounced as the duration of the annealing operation is "increasedfThis 'will" be apparent from the following table showing the effects of various annealing periods at a temperature of 1230 F; on colddrawn carbon-steel wires identical toeachother -except in respect to tlie pr's erice eratssenceb'f carbide forrhing metal} uration otanneal Wire v%ith- 0j03%V wire with my p.s.i.

"invention become more pronounced also asthe annealing temperature increases. Thus; varying the" temperature iinaintained'during a ten-second ant ater-motels-gram 'c'arborl 'teeIf wi r es "identical toj each fother'fexcept in r'e- 'pect tdth e presence'brabsence ofjca'r "f 'jing'me'tal gave'the followingresults:

The benefits obtainable 'through"employment tar-"my Wire with 0.20% .1

temperature v; (p.s.i.) (p.s.i.) 22285000 298,000 277,000 274,000 270, 000 254,000

(i In the following examples I show the effects resulting EXAMPLE 1 Base steel: 0.76% C; 0.79% Mn; 0.28% Si Added metal: 0.08% V Tensile strength Before anneal (p.s.i.) After anneal (p.s.i.)

Base steel wire. 283, 000 187, 000

Alloy-steel wire 253, 000 196, 000

EXAMPLE 2 Base steel: 0.79% C; 0.77% Mn; 0.31% Si Added metal: 0.20% V Base steel wire 298,000 198,000

Alloy-steel wire 285, 000 224, 000

EXAMPLE 3 Base steel: 0.78% C; 0.66% Mn; 0.23% Si Added metal: 0.33% Mo Base steel wire 298, 000 195, 000

Alloy-steel wire 259, 000 202, 000

EXAMPLE 4 Base steel: 0.74% C; 0.67% Mn; 0.28% Si Added metal: 0.36% Cr Base steel wire 283, 000 188, 000

Alloy-steel wire 289, 000 201, 000

EXAMPLE 5 Base steel: 0.72% C; 0.66% Mn; 0.25% Si Added metal: 0.17% W Base steel wire 269, 000 194, 000

Alloy-steel wire 269, 000 198, 000

EXAMPLE 6 Base steel: 0.74% C; 0.67% Mn; 0.28% Si Added metal: 0.05% Cb Base steel wire 328, 000 194, 000

Alloy-steel wire 317, 000 197, 000

Any of the carbide-forming metals may be used either alone or in combination with another or others to form alloys providing the advantage of this invention. Inclusion of a carbide-forming metal or metals in a proportion as low as 0.03% provides noticeable benefit in reducing the strength-loss suffered by cold-drawn carbon steel wire when subjected to annealing temperatures. Ordinarily, however, I prefer that the content of such metal or metals be at least 0.10%. As might be expected, and as is indicated for vanadium by Examples 1 and 2 above, the magnitude of the benefit resulting from use of my invention increases with increasing proportion of thescarbide-forming metal or metals; but considerations of cost, and in some cases the creation of undesirable side effects, put a practical limit of about 0.50% portion. In most instances, a proportion not greater than about 0.40% is preferred. Having regard for the effectiveness of the alloying metal in reducing the loss of tensile strength, for availability and cost, and for the nature of side effects produced, vanadium is probably the most desirable alloying metal, with molybdenum and" chromium following.

As between the latter two metals I on such prov g I prefer molybdenum; because, although a comparison of Examples 3 and 4 above shows that chromium is more effective than molybdenum in producing the benefit desired, relatively high percentages of chromium have an adverse effect on the drawability of the wire.

As above indicated, my invention is especially useful in the production of a cold-drawn wire which, after being coated with aluminum by passage through a molten bath of that metal, is to be used as a steel core wire in A.C.S.R. However, the invention is not limited to that application, as benefits of the type indicated result from its use in any cold-drawn carbon steel wire which, after being drawn, is subjected in use or further processing to temperatures high enough to result in a substantial decrease in tensile strength.

For high strength, such cold-drawn carbon steel wires should be made of a steel composition containing at least 0.50% carbon, and for the needed cold-drawing properties, the steel composition should not contain more than about 1.0% carbon.

It will be noted from the above examples that in each case the wire with added carbide-forming metal had, after subjection to a temperature of 1230 F. for ten seconds, a tensile strength appreciably greater than that of a similarly annealed wire of the same'composition except for omission of the carbide-forming metal. The loss of tensile strength, expressed in percent, was in each case less for each alloy-steel wire than for the corresponding base-metal wire, even in instances, such as those of Examples '4 and 5, where the addition of the carbide-forming metal either increased (Example 4) or was without significant effect (Example 5) on the tensile strength of the unannealed base-metal wire. 0n the average, the basemetal wires suffered a loss in tensile strength amounting to 34.2% as a result of the annealing operation, while the alloy-steel wires suffered a loss of only 27.3%. While the absolute gain of 3000 p.s.i. exhibited in Example 6 may appear relatively small, it is nevertheless important in view of the fact that 185,000 p.s.i. is about the minimum tensile strength permissible for the core wire of A.C.S.R. Thu's, that 3000 p.s.i. gain increased by one-third the margin over the minimum. In the case of Example 5, where the absolute gain was also small, the margin over the minimum was increased by about 44% I claim as my invention:

1. A cold-drawn, carbon steel wire of a carbon-steel composition consisting essentially of carbon in the proportion of from 0.5% to 1.0%, an alloying material consisting of one or more of the carbide-forming metals of the group consisting of chromium, tungsten, molybdenum, vanadium, and columbium. in the proportion of from 0.03% to 0.5 the balance being substantially iron, which cold-drawn wire has been subjected to a temperature of from approximately 800 F. to approximately 1300 F.

2. A cold-drawn, carbon steel wire as defined in claim 1 in which the alloying material is present in the proportion of from 0.1% to 0.4% of the composition.

3. The wire of claim 1 wherein the said alloying material consists essentially of vanadium.

4. The wire of claim 1 wherein the said alloying material consists essentially of molybdenum.

5. The wire of claim 1 wherein the said alloying material consists essentially of chromium.

6. The wire of claim 1 wherein the said alloying ma- "terial consists essentially of tungsten.

7. The wire of claim 1 wherein the said alloying material consists essentially of columbium.

I 8. A cold-drawn, carbon steel wire as set forth in claim 1 in which the wire has been subjected to said temperature by passing the cold-drawn wire through a bath of. molten aluminum and thereby coated with aluminum.

9. The wire of claim 2. wherein the said alloying material consists essentially of vanadium.

10. The wire of claim 2 wherein the said alloying material consists essentially of molybdenum.

11. The Wire of claim 2 wherein the said alloying material consists essentially of chromium.

12. The wire of claim 2 wherein the said alloying ma- 5 terial consists essentially of tungsten.

13. The Wire of claim 2 wherein the said alloying material consists essentially of columbium.

14. A cold-drawn, carbon steel Wire as set forth in claim 2 in which the wire has been subjected to said 10 temperature by passing the cold-drawn wire through a bath of molten aluminum and thereby coated with aluminum.

References Cited UNITED HYLAND BIZOT, Primary Examiner. P. WEINSTEIN, Assistant Examiner. 

